Hicks, B. J., & Tana, R. (2013). Life history analysis of chinook salmon (Oncorhynchus tshawytscha) from lakes Mapourika and Paringa, West Coast, South Island, New Zealand, by otolith microchemistry (ERI Report). Hamilton, New Zealand: Environmental Research Institute, The University of Waikato.
Permanent Research Commons link: https://hdl.handle.net/10289/13094
Otolith microchemistry is an established technique for determining fish migrations between the sea and freshwater. The aim of our study was to determine life history patterns of chinook salmon collected from rivers and lake tributaries along the West Coast of the South Island, New Zealand using otolith microchemistry. Specifically, we compared relative concentrations of barium and strontium in salmon otoliths as a proxy of fresh and seawater migration and related this to individual fish ages. Using this approach, fish migrations between the sea and freshwater are often determined by changing patterns in strontium (Sr) and barium (Ba) concentrations across the otolith growth axis. Time spent in the sea is characterised by high relative strontium and low barium concentrations, whereas freshwater phases have relatively higher barium and low strontium concentrations. When fish move from the sea to freshwater or vice versa a pronounced change in relative concentrations is usually seen. Ten chinook salmon were collected as carcasses or by fishing from the Hokitika and Taramakau rivers, Lake Mapourika and its tributary, MacDonalds Creek, and Lake Paringa and its tributary, Windbag Stream. A previous preliminary report investigated otoliths from 11 salmon captured in tributaries of lakes Mapourika and Paringa during 2008. This study showed lower ⁸⁷Sr/⁸⁶Sr ratios (0.707-0.709) that were interpreted as freshwater residence and higher ratios (0.710-0.712) that suggested sea residence. This approach uses strontium isotopic ratios instead of Sr and Ba elemental concentrations to determine freshwater and marine occupancy. Ratios of ⁸⁸Sr/V (vanadium) were also examined, and showed a reciprocal relationship to ratios of ⁸⁷Sr/⁸⁶Sr. All 11 otoliths examined from 2008 showed freshwater rearing followed by a period of marine residence of varying length. Chinook salmon in our study showed a wide variety of life histories, and microchemical analysis of the otoliths partly confirmed the presumed life history of each salmon. The freshwater phase was evident from strontium concentrations, expressed as ⁸⁶Sr/⁴³Ca x 1000, of between 100 and 400 and variable barium concentrations of between 2 to 8 expressed as ¹³⁷Ba/⁴³Ca x 1000. The marine phase was characterised by high strontium concentrations of 500 to 900, with low barium concentrations, generally less than 2. Five individuals from the Hokitika and Taramakau rivers, MacDonalds Creek (L. Mapourika), and Windbag Stream (L. Paringa) exhibited normal chinook salmon life histories with early rearing in freshwater followed by an extensive period of growth to adulthood in the sea. Most salmon from MacDonalds Creek showed extensive freshwater residence, and two of these were lakelocked, with exclusively freshwater residence. A further two fish collected in May 2012 from MacDonalds Creek had lived most of their life in freshwater but showed evidence of a brief period in the sea late in life at ages 2 and 3 year respectively. Curiously, one fish from MacDonalds Creek had apparently entered a marine environment, possibly an estuary, just before its recovery as a carcass.
Environmental Research Institute, The University of Waikato